From the Desk of Ed Hume: Spring Flowering Rhododendrons

April 3, 2011 at 11:49 PM Leave a comment

If you were to drive into our driveway today, you would be greeted by three magenta flowering PJM rhododendrons and several magenta and white winter flowering heather in full bloom.  What a sight!  They offer summer color in the spring and both plants are evergreens, so they grow bigger and more beautiful each year.  In this article, let’s discuss how to care for the beautiful rhododendrons (Remember, we talked about winter heather earlier. You can get more information on heather at

Rhododendrons are especially popular in the landscape because of their beautiful flowers, leaf textures, various growing heights, and evergreen foliage.  There are thousands of rhododendron varieties with flower trusses in varying colors which practically span the entire color spectrum.  Flowers vary in size from some that are smaller than a marble to others that are almost as large as a volleyball.  Plants vary in size from as low as six inches high to some that will grow up to 30 feet or more at maturity.  Likewise, leaves vary from very small to some that are about twelve inches long.

Rhododendrons grow and flower best in the shady part of the garden.  Some will grow in part sun and shade, and there are just a few that will tolerate full sun in a cool climate.

Some of the species varieties of rhododendron have bluish leaves, while most larger ones have green leaves.  A couple varieties have attractive variegated green and yellow leaves.

Here are a few hints on growing rhododendrons in a northwest garden:

SELECTING YOUR PLANT: I think the best time to choose a variety for your garden is when the plants are in bloom.  Say you want a red one; there are so many shades of red that if you don’t see it in bloom and see the actual color, you may not be happy with your selection when it begins to flower.

PLANTING SUGGESTIONS: As mentioned earlier, this is one plant that likes shade or part sun and shade.  It must be planted so the top of the root ball is right at ground level.  If it is planted or mulched too deeply, it will grow but will not flower.  Plants need a planting location with good drainage.  At planting time, add organic humus with the existing soil.  Compost, well rotted manure (the bagged stuff), and/or peat moss are excellent sources of organic matter.

FERTILIZING: I feed my rhododendrons only when they need it.  If the leaves begin to be a bit off color or if growth begins to diminish, these are signs for the need to fertilize.  Use a rhododendron or evergreen type of plant food for rhododendrons, camellias, and azaleas.  Immediately after plants flower is the best time to feed them.

WATERING: During warm weather, the plants need at least one inch of water per week.  If the leaves begin to lose their luster or begin to wilt a bit, increase the amount of water you are giving them.  Plants should never sit in water over winter or in early spring.

PRUNING: If needed, the best time to prune or shape them is immediately after they have finished flowering.  Severe pruning will result in the loss of flowers for at least one year.

TRANSPLANTING: If you need to transplant an established plant, it is best done during November, December, January, February, or earliest March, weather permitting.

PICK OFF DEAD FLOWERS: As soon as the flower die, they should be picked. If the spent flowers are left on the plant, it seems to affect the new growth and flowers for the next year.

For more information on rhododendrons, refer to my latest garden book, Gardening With Ed Hume: Northwest Gardening Made Easy.  More info on my book can be found here.


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Clip of the Week: Fertilizing the Garden Ed’s Podcasts: Azaleas

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